Although low molecular weight substances, nucleic acids, proteins, nano-particles, etc., have great potentials as therapeutic substances at a molecular level, their uses are limited due to the incompetence to penetrate into tissues and cell membrane. The development of a system to deliver such substances into the cell has been the active area of research over the last two decades. Transporting the substances inside the cell has been a conversation topic in a treatment of molecular method. Low-molecular weight substances, nucleic acids or nano-particles were transported inside the cell by several reagents, electroporation or heat shock. However, it was difficult to find an adequate method of delivery of proteins inside the cell without disrupting the activity and integrity of proteins. In the 1980s, in the research conducted on studying the cell penetrating capacity of HIV, it was found that HIV-TAT protein consisting of specific 11 amino acids play an important role in a process of transportation inside the cell. Thus, since 1990s, studies on finding the right method of transporting proteins inside the cell has been the intense area of research.
Telomere is known as a repetitive sequence of genetic material found at the ends of chromosomes that prevent chromosomes from damage or merging onto other chromosomes. The length of the telomere is shortened at each cell division, and after a certain number of cell division, the telomere length is extremely shortened to the extent in which the cell stops dividing and dies. On the other hand, the elongation of telomeres is known to extend the life span of a cell. For an example, cancer cells excrete an enzyme called telomerase, which prevents shortening of telomeres, thus resulting in proliferation of cancer cells.
STAT3 inhibitors regulate tumors by complexed anti-tumor mechanism including apoptosis, inhibition of angiogenesis and blockage of immune evasion. It is reported that NSC74859, which is a STAT3 inhibitor drug, has dose-dependent side effect when it is administrated. So, there is the need for the method of suppression of cancers by administrating low dose of the drug.
Paclitaxel is used for treating ovarian cancer, breast cancer, lung cancer or gastric cancer and it is reported that paclitaxel has dose-dependent side effect, which is decreases of leucocytes, erythrocytes, and thrombocytes by bone marrow suppression. So, there is the need for the method of treating cancers more efficiently by administrating low-dose paclitaxel.